Excerpted response below from my email to the head of DEI where I work; my question and his answer.
Tempted to respond by saying "Humans don't change sex".
Just to confirm – does this mean that [this higher education institution] are no longer offering single-sex facilities at the study centres?
No – there is no change to our facilities, [the higher education institution] are continuing to provide single-sex facilities. Trans men may use male designated toilets and Trans women may use female designated toilets, as is our current policy. We are also investigating the possibility of our accessible toilets broadening their scope so that they may be used as a gender-neutral, single-lockable space.